1. Field of the Invention
The present invention relates to a vehicle running control system in which, even in a case in which a target object is not recognized as a preceding vehicle, when a fixed condition is satisfied, the target object is regarded as a preceding vehicle and a subject vehicle is caused to follow the target object.
2. Description of the Related Art
In recent years, various proposals have been made for vehicle drive assist systems in which an outside environment in front of a subject vehicle is recognized by a front-environment recognition device such as a millimeter-wave radar, an infrared laser radar, a stereo camera, or a monocular camera, and in which running of the subject vehicle is controlled on the basis of the recognized outside environment.
One of these vehicle drive assist systems is an inter-vehicle distance control (ACC; Adaptive Cruse Control) system. The ACC system performs constant-speed running control so that a subject vehicle travels at a vehicle speed set by the driver (set vehicle speed) and follow-up running control so that the subject vehicle follows a preceding vehicle, in accordance with the result of recognition of the preceding vehicle.
The ACC system determines, according to information from a front-environment recognition device, whether or not the preceding vehicle is traveling in a traveling region of a traveling path of the subject vehicle. When the preceding vehicle is detected, the ACC system registers the preceding vehicle, and performs follow-up running control so that the subject vehicle follows the registered preceding vehicle at a constant distance and a constant speed relative to the preceding vehicle, by using throttle control or brake control. In contrast, when the preceding vehicle is not detected, the ACC system performs constant-speed running control so that the subject vehicle travels at the speed set by the driver. For example, the ACC system is disclosed in Japanese Unexamined Patent Application Publication No. 2003-308598 (Patent Document 1).
In a case in which a preceding vehicle to follow is registered, if all three-dimensional objects present in the traveling region, which is set in front of the subject vehicle and centered on the traveling path of the subject vehicle, are selected as candidates for target objects, for example, when the subject vehicle enters a curve, stationary three-dimensional objects, such as guardrails standing on the sides of the curve and vehicles stopped outside the curve, are also selected as candidates. As a result, when the subject vehicle comes close to the stationary three-dimensional objects, an unnecessary braking operation is performed.
On the other hand, for example, when the preceding vehicle serving as a target object stops at a red light, it is also regarded as a stationary three-dimensional object and is removed from candidates for target objects. In this case, the subject vehicle following the preceding vehicle is not controlled by the ACC system even when the subject vehicle comes close to the stopped preceding vehicle. Hence, unless the subject vehicle is decelerated by a braking operation of the driver or by an automatic brake control device, the subject vehicle cannot be stopped at an appropriate inter-vehicle distance from the preceding vehicle.
In such a case in which the stopped preceding vehicle is excluded from candidates for target objects in the ACC system although it is recognized by the driver or in which stationary three-dimensional objects, such as guardrails in front of the subject vehicle and vehicles stopped outside the road, are registered as target objects although they are not recognized as the preceding vehicle by the driver, control is performed against the driver's intention. This gives the driver a feeling of discomfort.